A few Floridian friends of mine review all my votes before I actually cast them. They know how I 'really' meant to cast my vote when oftentimes I don't. Thank goodness there is no such thing as a pregnant chad in the monastery!

Sometimes after voting a ++, I'll try to use the down arrow key to scroll down to the vote! button. This changes my vote to --. I'm used to using the arrow keys to scroll a web page.
This trips me up every now and then.

Sometimes after voting a ++, I'll try to use the down arrow key to scroll down to the vote! button.
I did this a few times at first, but soon learnt that it was best not to do it this way. My error rate would be < 1%, now that I have got that coordinated

I guess my error rate is actually 0%, since I've never voted -- on anything. My preference is to simply ++ those nodes I believe are worthwhile, either because they ask good questions or present good information. Thus far, I've always found enough good posts to use all of my votes on. ;) It's better, IMNSHO, to encourage our fellow monks who post positive contributions this way than to worry about "punishing" the negative contributions via --.

But that's not what the poll is asking. Even if you only ever vote ++ (or -- for that matter) you may sometimes vote for something you didn't intend to. That would be an "unintended vote" as much as voting the wrong way.

Perhaps, after someone votes, a link can appear under the reputation listing, with the text "Change Vote" or similar. This would link to a form to change the vote.
The idea here is that it's possible to change a vote, while making it a non-trivial process, so people would be less inclinded to change after simply seeing the way others have voted
(which is, I assume, why one can't see the reputation score until they vote).

Spacewarp

DISCLAIMER:
Use of this advanced computing technology does not imply an endorsement
of Western industrial civilization.

You have to be careful here. Part of the reason the reputation isn't shown before monks vote on a node is so as not to influence the voting, as you say. If you can arbitrarily change your vote after casting it (with no penalty; I'm not sure how the form you suggest would work.) then this problem pops up, albeit on a much smaller scale.

First off if this misvoting is a serious concern, then it should be possible to at least print how you voted next to the rep. This could be done only immediately after the vote, unless the database is reworked to record each and every vote ever cast. (As opposed to currently, where I suspect it is only recorded that you voted, not how you voted, although this is only a suspicion.)

If in fact it is recorded how you vote, then changing a vote would be easier to implement, but you should be penalized if you decide to change your vote. Say by using up an extra vote to change an old vote. Additionally, some thought would have to be given to how this would affect the experience of the writer of the node in question.

I think consuming an extra vote alone won't do it - especially on higher levels you have enough daily votes that it won't make a difference. It is a very rare day that I manage to spend all my 40 votes, and even with 30 at level 8 I often had a few left over at the end of the voting day.

I was going to propose it should cost an XP, but both penalties at once would be even better. If it is at all implemented (and I don't think I like the idea), then it should really hurt to take the offer. The message should clearly be "pay attention next time, and don't get used to this feature".